1. Field of the Invention
This invention relates to the diagnosis and treatment of cardiac arrhythmias. More particularly, this invention relates to the identification of arrhythmogenic foci associated with ventricular tachycardia.
2. Description of the Related Art
TABLE 1Acronyms and AbbreviationsDACDigital-To-Analog ConverterECGElectrocardiogramEEGElectroencephalogramFFTFast Fourier TransformICAIndependent Component AnalysisICDIntracardiac DeviceISInduced Electrocardiographic SignalsMin-PMLMinimum Number of LeadsPCAPrincipal Component AnalysisPMPace-Mapped Electrocardiographic SignalsPMCTPace-Mapped Correlation ThresholdQLQualifying LeadsVTVentricular TachycardiaWOIWindow of Interest
Cardiac arrhythmias such as ventricular tachycardia are an important cause of morbidity and death. Commonly assigned U.S. Pat. No. 5,546,951, and U.S. Pat. No. 6,690,963, both issued to Ben Haim; and PCT application WO 96/05768, all of which are incorporated herein by reference, disclose methods for sensing an electrical property of heart tissue, for example, local activation time, as a function of the precise location within the heart. Data are acquired with one or more catheters having electrical and location sensors in their distal tips, which are advanced into the heart. Methods of creating a map of the electrical activity of the heart based on these data are disclosed in commonly assigned U.S. Pat. No. 6,226,542, and U.S. Pat. No. 6,301,496, both issued to Reisfeld, which are incorporated herein by reference. As indicated in these patents, location and electrical activity is typically initially measured on about 10 to about 20 points on the interior surface of the heart. These data points are then generally sufficient to generate a preliminary reconstruction or map of the cardiac surface. The preliminary map is often combined with data taken at additional points in order to generate a more comprehensive map of the heart's electrical activity. Indeed, in clinical settings, it is not uncommon to accumulate data at 100 or more sites to generate a detailed, comprehensive map of heart chamber electrical activity. The generated detailed map may then serve as the basis for deciding on a therapeutic course of action, for example, tissue ablation, to alter the propagation of the heart's electrical activity and to restore normal heart rhythm.
Catheters containing position sensors may be used to determine the trajectory of points on the cardiac surface. These trajectories may be used to infer motion characteristics such as the contractility of the tissue. As disclosed in U.S. Pat. No. 5,738,096, issued to Ben Haim, and incorporated herein in its entirety by reference, maps depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart.
U.S. Pat. No. 6,847,839, issued to Ciaccio, et al., describes a method for identifying and localizing a reentrant circuit isthmus in a heart of a subject during sinus rhythm, including: a) receiving electrogram signals from the heart during sinus rhythm via electrodes; b) storing the electrogram signals; c) creating a map based on the electrogram signals; d) finding a center reference activation location on the map; e) defining measurement vectors originating from the center reference activation location; f) selecting from the measurement vectors a primary axis vector indicating a location of the reentrant circuit isthmus in the heart; g) finding threshold points of electrogram signals on the map; h) connecting the threshold points to form a polygon indicating a shape of the reentrant circuit isthmus in the heart.